This invention relates to an apparatus for maintaining the environment of developer material in a developer housing at a predefined set point.
Generally, the process of electrophotographic printing includes charging a photoconductive member to a substantially uniform potential to sensitize the photoconductive surface thereof. The charged portion of the photoconductive surface is exposed to a light image from either a scanning laser beam, an LED source, or an original document being reproduced. This records an electrostatic latent image on the photoconductive surface. After the electrostatic latent image is recorded on the photoconductive surface, the latent image is developed. Two-component and single-component developer materials are commonly used for development. A typical two-component developer comprises magnetic carrier granules having toner particles adhering triboelectrically thereto. A single-component developer material typically comprises toner particles. Toner particles are attracted to the latent image, forming a toner powder image on the photoconductive surface. The toner powder image is subsequently transferred to a copy sheet. Finally, the toner powder image is heated to permanently fuse it to the copy sheet in image configuration.
The electrophotographic marking process given above can be modified to produce color images. One color electrophotographic marking process, called image-on-image (IOI) processing, superimposes toner powder images of different color toners onto a photoreceptor prior to the transfer of the composite toner powder image onto a substrate. While the IOI process provides certain benefits, such as a compact architecture, there are several challenges to its successful implementation. For instance, the viability of printing system concepts, such as IOI processing, require development systems that do not interact with a previously toned image. Since several known development systems, such as conventional magnetic brush development and jumping single-component development, interact with the image on a receiver, a previously toned image will be scavenged by subsequent development if interacting development systems are used. Thus, for the IOI process, there is a need for scavengeless or noninteractive development systems.
Hybrid scavengeless development technology develops toner via a conventional magnetic brush onto the surface of a donor roll and a plurality of electrode wires are closely spaced from the toned donor roll in a development zone. An AC voltage is applied to the wires to generate a toner cloud in the development zone. The donor roll generally consists of a conductive core covered with a thin (50-200 .mu.m) partially conductive layer. The donor roll is held at an electrical potential difference relative to the conductive core to produce the field necessary for toner development. The toner layer on the donor roll is then disturbed by electric fields from a wire or set of wires to produce and sustain an agitated cloud of toner particles. Typical AC voltages of the wires relative to the donor roll are 700-900 Vpp at frequencies of 5-15 kHz. These AC signals are often square waves, rather than pure sinusoidal waves. Toner from the cloud is then developed onto a nearby photoreceptor by fields created by a latent image.
A problem with developer systems is that when the temperature of a material is not in control results in increase contamination; donor roll filming, particles forming on electrode wires, material migration through a xerographic. cavity, toner spitting, low image density, and poor/changing material transfer characteristics.
There is provided an apparatus for developing a latent image recorded on a movable imaging surface, including a reservoir for storing a supply of developer material including toner particles; a donor member being arranged to receive toner particles from said reservoir and to deliver toner particles to the imaging surface at locations spaced apart from each other in the direction of movement of the imaging surface thereby to develop the latent image thereon; and a climate system, associated with said reservoir, for maintaining said supply of developer material at a predefined temperature.
There is also provided an electrostatic printing machine having an apparatus for developing a latent image recorded on a movable imaging, surface, including a reservoir for storing a supply of developer material including toner particles; a donor member being arranged to receive toner particles from said reservoir and to deliver toner particles to the imaging surface at locations spaced apart from each other in the direction of movement of the imaging surface thereby to develop the latent image thereon; and a climate system, associated with said reservoir, for maintaining said supply of developer material at a predefined temperature.
There is also provided a method for maintaining the environment of developer material in a developer housing at a predefined set point comprising: sensing the temperature of said supply of developer material; and selectively activating and de-activating a heating element or a cooling element based on the temperature sensed.
While the present invention will hereinafter be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.